Fix bug with missing baked SDF data on save when asset data chunk memory was freed by GC

Source/Engine/Content/Assets/Model.cpp

@@ -682,7 +682,11 @@ bool Model::GenerateSDF(float resolutionScale, int32 lodIndex, bool cacheData, f
 #if USE_EDITOR
     // Set asset data
     if (cacheData)
-        GetOrCreateChunk(15)->Data.Copy(sdfStream.GetHandle(), sdfStream.GetPosition());
+    {
+        auto chunk = GetOrCreateChunk(15);
+        chunk->Data.Copy(sdfStream.GetHandle(), sdfStream.GetPosition());
+        chunk->Flags |= FlaxChunkFlags::KeepInMemory; // Prevent GC-ing chunk data so it will be properly saved
+    }
 #endif
 
     return false;

Source/Engine/Content/Storage/FlaxChunk.h

@@ -11,7 +11,7 @@
 enum class FlaxChunkFlags
 {
     /// <summary>
-    /// The none.
+    /// Nothing.
     /// </summary>
     None = 0,
 
@@ -19,6 +19,11 @@ enum class FlaxChunkFlags
     /// Compress chunk data using LZ4 algorithm.
     /// </summary>
     CompressedLZ4 = 1,
+
+    /// <summary>
+    /// Prevents chunk file data from being unloaded if unused for a certain amount of time. Runtime-only flag, not saved with the asset.
+    /// </summary>
+    KeepInMemory = 2,
 };
 
 DECLARE_ENUM_OPERATORS(FlaxChunkFlags);

Source/Engine/Content/Storage/FlaxStorage.cpp

@@ -943,7 +943,8 @@ bool FlaxStorage::Create(WriteStream* stream, const AssetInitData* data, int32 d
     {
         FlaxChunk* chunk = chunks[i];
         stream->WriteBytes(&chunk->LocationInFile, sizeof(chunk->LocationInFile));
-        stream->WriteInt32((int32)chunk->Flags);
+        FlaxChunkFlags flags = chunk->Flags & ~(FlaxChunkFlags::KeepInMemory); // Skip saving runtime-only flags
+        stream->WriteInt32((int32)flags);
     }
 
 #if ASSETS_LOADING_EXTRA_VERIFICATION
@@ -1410,7 +1411,7 @@ void FlaxStorage::Tick(double time)
     {
         auto chunk = _chunks.Get()[i];
         const bool wasUsed = (time - chunk->LastAccessTime) < unusedDataChunksLifetime;
-        if (!wasUsed && chunk->IsLoaded())
+        if (!wasUsed && chunk->IsLoaded() && EnumHasNoneFlags(chunk->Flags, FlaxChunkFlags::KeepInMemory))
         {
             chunk->Unload();
         }